USES: This valve for living systems, industrial water supply system, especially in fire control system for the water effect is extremely good. Working principle: The main valve seal linkage pieces by hydraulic pipe pressure transmission imitate guide valve movements, When the outlet pressure below the set value, guide valve opens, The diaphragm above control indoor pressure water is discharged to small swim(emission speed is greater than the inlet stream supplement speed) The main valve seal linkage, make up for a little outlet pressure increases to value When export pressure is higher than setting, guide valve is closed, The diaphragm above control indoor pressure water downward effect on the diaphragm, The main valve seal linkage thing moving downward, make a little outlet pressure to reduce value.